Method of and system for electrical signaling



Dec. 11, 1928.

J. H. HAMMOND, JR

METHOD OF AND SYSTEM FOR ELECTRICAL SIGNALING Filed Feb. 12, 1925 3 Sheets-Sheet INVENTOR llllll A 0ND JR,

HAY

ATTORNEY Dec. 11,1928. 1,694,654

J. H. HAMMOND, JR

METHOD OF AND SYSTEM FOR ELECTRICAL SIGNALING Filed Feb. 12, 1925 .s Sheets-Sheet 2 lllll:

A ORNEY JOHN HAY AMM ND R.

Dec. 11, 1928.

J. HAMMOND, JR

METHOD OF AND SYSTEM FDR ELECTRICAL SIGNALING 3 Sheets-Sheet Filed Feb. 12, 1925 'INVENTOR V JOH ,AYS AM 0ND JR.

d/fl f TORNEY Pfldhtid on. 11,1928

UNITED srarss PATENT OFFICE.

JOHN HAYS HAMMOND, JR, OF GLOUCESTER, MASSACHUSETTS;

unrnon or AND SYSTEM For. Emcrmcni srenaame'.

Application filed February 12, 1925. serial n. 8,644.

sent in such a manner that they cannot be intelligibly. received by receivers not constructed in accordance with the invention but can be readily and reliably received by receivers made in accordance with the invention.

An iniportant object of the invention is to utilize changes in phase of electrical oscillations to enable the provision of a method of and system for electrical signaling having the above-mentioned and other advantages.

To this end, an-important feature of the inventon resides in the provision of means for producin and transmitting electrical oscillations 0 a substantially constant-high frequency and means for changing the phase of the oscillations in accordance with signals. Preferably and in the present embodiment of the invention, means are also provided for amplifying-the oscillations and the means for changin the phase of the oscillations is lIItGIPOSBd TJGtWBQII the produc- 'ing means and the amplifying means.

In accordance with another feature of the invention, a circuit is provided comprising branch inductive and capacitive circuits connected in parallel, and a reactance device arranged to be difierentially coupled with the branch circuits respectively is connected in a fourth circuit so as variably to determine the phase of current supplied to the lastmentioned circuit. The fourth circuit may be the grid-filament circuit of a three-electrode vacuum tube, and the differential connections between the grid-filament or input circuit of the tube and the branch inductive and capacitive circuits respectively may be employed to determine the phase of the oscillations set up in the output circuit of the tube.

A still further feature of the invention contemplates the provision of means for transmitting oscillations successively in different phases in accordance with signals and a receiver including means for' neutralizing oscillations transmitted in one phase and for causing an indicator to be operated by the received oscillations in accordance with their signal modifications. The means for neutralizing the oscillations of the last-mentioned phase may conveniently be a local source of oscillations of the same frequency as the transmitted oscillations.

In'order to enable the advantages of this invention to be best attained, it is necessary that the oscillations produced at the receiver shall be as nearly as possible of the same frequency as those generated at the transmitter. Accordingly, piezo-electric oscillators of the same frequency are provided at the transmitter and receiver, it being well known in the art that such oscillators may be employed to produce oscillations of a frequency which is either absolutely constant or very nearly so. 1

Still other objects and features of the invention will a pear as the description'proceedsand will e pointed out in the appended claims. i

In the drawings,

Fig. 1 is a diagrammatic representation of a transmitter constructed in accordance with the inventlon;

Fig. 2 is adetail view of the keying mechanism of the transmitter;-

Fig. 3 is a diagrammatic representation of a receiver constructed according to the invention;

Fig. 4 is a diagrammatic representation of a receiver of modified form; and

Fig. 5 is a view of a detail of the'receiver.

The transmitter shown in Fig. 1 comprises in general a piezo-electric oscillator designated generally by 10, phase-changing means 12, a vacuum tube amplifier 14, preferably a so-called power amplifier, and an antenna 16.

The piezo-electric oscillator 10 comprises a three-electrode vacuum tube 18 containing a plate 20, a grid 22, and a filament 24, the latter being heated in the usual manner by a battery 26 acting through a rheostat 28. The grid-filament circuit of the tube 18 includes a resistance 30, and the output circuit of the tube includes a high potential battery 32 and the primary windlng 34 of a transformer 36. A piezo-electric crystal 38 is connected be-. tween the plate 20 and grid 22 of thevacuum tube 18. The crystal 38, may, for example, be a piece of quartz interposed between plates 40 and 42 of suitable conducting material, such as brass.

A piezo-electric oscillator similar to the oscillator 10 is more fully described in a paper by George W. Pierce published in, lines 81 to 106 inclusive of the Proceedings of the American Academy of Arts and Sciences, vol. 59, No. 4-October, 1923, and entitled Piezoelectric cr stal resonators appliedto the precision calibration of wave meters.

The phase-changing means 12 includes a closed circuit 44 comprising the secondary winding 46 of the transformer 36 and branch inductive and capacitive circuits 48 and 50 respectivel connected in parallel. As shown, the in uctive circuit 48 comprises a resistance 52 and coils 54 and 55, and the capacitive circuit 50 comprises a resistance 56, a condenser 58 and coils 59 and 60. The branch circuit 48 is preferably so constituted as to produce a lag of substantially 45 in the phase of oscillations passed through it, and the capacitive circuit 50 is preferably so constituted as to produce a lead of substantially 45 in the phase of oscillations passed through it. The impedances of the inductive circuit 48 and capacitive circuit 50 to the current produced b the piezo-electric oscillat or 10are preferably substantially equal so as to cause equal currents to flow in the coils 54 and 55, on the one hand, and the coils 59 and 60 on the other.

The phase-changing means 12 further comprises a reactance device 62 arranged to be difierentially coupled with the coils 54, 55 and 59, 60, and connected in a circuit 64. As shown, the reactance device 62 has the form of a rotor coil mounted on an operating shaft 63, and the coils 60, 54, 59 and 55 are arranged around the periphery of the rotor coil 62 at distances apart of 90 respectively. From the foregoing, it will be understood that when the rotor coil 62 occupies the position shown in Fig. 1 of the drawings oscillations are supplied to the circuit 64 in one phase and that when the coil 62 is rotated through an angle of 180 from its illustrated osition, the phase of the oscillations supplied to the circuit 64 is gradually changed through 180.

The amplifier 14 comprises a vacuum tube having a usual plate 68, grid 7 0 and filament 72 heated by a battery 7 4, the current from which is controlled by a rheostat 7 6. As shown, the circuit 64 in which the rotor coil 62 of the phase-changing means 12 is connected constitutes the grid-filament circuit of the vacuum tube amplifier 14.

The output circuit of the amplifier 14 includes a high potential battery 7 8 and the primary winding 80 of a transformer 82, the secondary winding 84 of whichis connected between the antenna 16 and ground 86, so that oscillations produced in the output circuit of the amplifier 14 are transferred to the antenna 16, which in turn produces corresponding etheric oscillations.

In order to modify the energy radiated from the transmitter shown in Fig. 1 in accordance with signals, the coil 62 may be rotated thereby causin the phase of the oscillations radiated by die antenna 16 to be shifted with respect tothe plate current of the piezo-electric oscillator 10. Preferably, the coils 54, 55, '59 and 60 are so arranged as to produce a rotating field of constant strength so that the inner coil 62 receives the same amount of peak flux regardless of itsorientation, with the result that rotation of the coil 62 does not vary the total amount of current induced in it from the coils 54, 55, 59 and 60 and, consequently, does not aifect the am-- plitude of the oscillations radiated by the antenna 16. This condition may be achieved by causing the currents in the two primaries 54, 55 and 59, 60 respectively of the coil 62 to be of equal strength and displaced exactly by 90 in phase, by having a sine Wave relation between flux from primary to secondary as the secondary is rotated, and further locating the coils of the system at right angles and in the same plane. The arrangement of thephase-changing means 12 so that rotation of the coil 62 does not cause variation in the amplitude of the transmitted oscillations is of importance in preventing reception of signals by receivers of known types, for reasons which will be manifest to those skilled in the art.

Signals may be sent by direct, manual rotation of the shaft 63 of the rotor coil 62. Preferably, however, mechanism is provided whereby signals may be sent by manipulation of a key in the manner usual in telegraphy. In the form of such mechanism shown in Fig. 2 of the drawings, the shaft 63 of the rotorcoil 62 is provided with a gear 88 meshing with a second gear 90 which in turn meshes with teeth on a rack bar 92. One end of the rack bar 92 enters a solenoid coil 94 through which current may be passed from a battery 96 upon closure of a control key 98. Upon deenergization of the solenoid coil 94, the rack bar 92 is returned to normal position by a spring 100. A variable-speed dash-pot 102 is preferably provided to dampen or cushion the movements of "the rack bar 92 under the influence of the solenoid coil 94 and spring 100. As shown, this dash-pot comprises a chamber containing air or other gas and having ports governed by adjustable valves 103 and 1,04, and a piston 106 is operatively connected to the rack bar 92 and is arranged .to move in the chamber of the dash-pot 102 be tween the above-mentioned ports.

The receiver illustrated in Fig. 3 comprises an antenna 110 grounded at 112 and containing the primary winding 114 of a transformer 116. The secondary winding 118 of the transformer 116 is connected in a closed, oscillatory circuit 120 which also includes a variable condenser 122. The oscillatory circuit 120 is preferably tuned to the high frequency oscillations radiated by the transmitter and is cony a usual battery 130, and the amplifier 128 is provided with a plate'132 and an output with the grid 1% and filament 1 sv respectively of a three-electrode, vacuum tube ainlifier 128. The filament 126 may be heated circuit including a'high potential battery134 and a coil 136.

Coupled with the coil 136, of theamplifier 128 is a coil 138 connected in the input circuit 139 of a detector 140 which controls a suitable indicator 142. The indicator, as shown, is in the form of telephones.

Also coupled with the coil 138 of the detector 140 is a coil 144 arranged inthe delivery circuit of a piezo-electric oscillator 146. The iezo-electric oscillator 146 may be identical in construction with the piezo-electric oscillator 10 at the transmitter. Accordingly, the oscillator 146 does not require detailed description.

The piezo-electric oscillator 146 is designed to produce electrical oscillations of the same frequency as those produced by the piezoelectric oscillator 10 at the transmitter. *In order to achieve this purpose, the crystal 148 of the oscillator 146 is so chosen as to cause its natural frequency of vibration to be the same as that of the crystal 38 of the oscillator 10. This may be done by employing as crystals 38 and 148 parallelopiped sections of a single large crystal cut to the same dimensions. The couplings between coils 136 and 138 and between coils 138 and 144 respectively are preferably made variable for a purpose which will hereinafter appear.

A vacuum tube oscillator 150 of known form is coupled to the input circuit 139 of the detector 140 by windin s 152 and 154 to afford a convenient source 0 oscillations of a frequency such as to produce audible beats with high frequency oscillations impressed on said detector by the amplifier 128.

In Fig. 4 is shown a receiving arrangement of modified form comprising an antenna 210,-

an amplifier 228, a detector 240 having its input circuit adjustably coupled with the output circuit of the amplifier by coils 230 and 232, an indicator 242, a heterodyne oscillator 244 and a piezo-electric oscillator 246 of thev kind shown in Figs. 1 and '2 and hereinbefore described. In this embodiment of the invention, a phase-changing device 248 analogous to the phase-changing device 12 of Fig. 1 is interposed between the piezo-electric oscillator 246 and the detector 240.

The phase-changin means 248 includes a closed circuit 250 coup ed with the piezo-elec- 'tric oscillator 246 and branch inductive and capacitive circuits 252 and 254 respectively connected in parallel. As shown, the inductive circuit- 252 comprises a resistance 256 and coils 258 and 260, and the capacitive circuit 254 comprises a resistance 262, a condenser 264 and coils 266 and 268. The branch inductive circuit 252 is preferably so constituted as to produce a lag of substantially in the phase of oscillations passed throng it, and the ca acitive circuit is preferab so constitute as to produce a lead of substantially 45 in the base of oscillations passed through it. he phase-changing means 248 further comprises a rotor coil 270 arranged to be difierentially coupled with the coils 258, 260 and 266, 268 and connected in a circuit 272. The coils 266, 258, 268 and,

of the coil 27 0 through an angle of 180 from its illustrated position, the phaseof the oscilv lations'sup lied to the circuit 272 maybe gradually c anged through 180. The circuit 272 contains a coil 274 adjustably coupled with the coil 232 in the input circuit of the detector 240. I

In the operation of the transmitter shown in Fi 1, assuming that the key 98 is open and te rotor coil 62 is in the position indicated in Fig. 1, oscillations are transmitted in a phase which lags'behind the phase of the oscillations delivered by the plezo-electric oscillator 10 by substantially 45. The transmitted oscillations tend to produce oscillations of like frequency in the output circuit of'the amplifier 128 of the receiver shown in Fig. -2. In order, however, to prevent oscillations transmitted in this phase from operating the indicator 142, the iezoelectric oscillator 146 which, as exp ained above, generates oscillations of the same frequency as the transmitted oscillations and is adjustably coupled to the input circuit 139 of detector 140 by the coils 138 and 144 may be caused to dehver to the in ut circuit of the detector 140 oscillations o a phase and amplitude such as to neutralize the effect of the transmitted oscillations. In such a case, the indicator 142 would not be afiected by oscillations transmitted in the above phase.-

an angle of 180, the phase of the transmitted oscillations. is changed continuously to a value 180 difi'erent from the initial phase. The received oscillations then set up current in the output circuit of the amplifier 128 and the input circuit of the detector 140 of phases such that the current is not neutralized by the oscillations produced by the piezo-electric oscillator 146. On the contrary, under the last-mentioned conditions of transmission, the oscillations locally produced by the piezo-electric oscillator 146 may add thelr effect to that of the current set u -in the coil 138 by the received oscillations. nder the conditions last-described current of the high signal frequency is set u in the input circuit of the detector 140. and t e heterodyne oscillator 150, together with the detector 140, causes such currents to produce an audible note in the telephones 142. Accordingly, closing of the key 98 of the transmitter, under the conditions assumed causes the indicator 142 to be operated by the combined effect of current produced by the local piezo-electrlc oscillator 14:6 and the current set up in the 0011 138 of the detector 140 by the received oscillations.

The operation of the transmitting and receiving arrangement is substantially the same when a receiver such as is shown in Fig. i is used in place of that illustrated in Fig. 3. The phase-shifting means 248 of Fig. 3, however, enables the oscillations produced byvthe local piezo-electric oscillator 24:6 to be impressed upon the input circuit of the detector 240 in precisely the phase required to cause the locally-produced oscillations to neutralize the transmitted oscillations in the desired position of the key 98. Moreover, if

ment of the rotor coil 270 of the phase-shiftin'g means 248. To facilitate its adjustment the shaft 269 of the rotor coil 270 may, of course, be provided with a knob 27 2 or other handle device, Fig. 5.

We have assumed above that a piezo-electric oscillator 246 is provided at the receiver which produces oscillations of the same frequency as those produced by the piezo-electric oscillator 10 of the transmitting station.

It may, however, under some conditions of the use of the invention be more desirable to employ at. the receiver an oscillator which produces oscillations which are not of exactly the same frequency as those radiated from the transmitter. In such an event, the rotor coil 62'of the transmitter, or the coil 27 O of the receiver shown in Fig. 4 may be continuously rotated at a speed correspond ing to the difl'erence in the frequencies of the oscillators 10 and 246 in order to synchronize perfectly the transmitted and locally-produced oscillations. enabling applicants invention to be employed in a system in which the oscillations produced at the receiver are not of exactly the same frequency as the transmitted oscillations is illustrated in Fig. 5, wherein the shaft 269 of the rotor coil 270 has keyed A convenient means forlations of a high frequency substantial htttttt thereto a slidable clutch element 2T4- which, at the will of the operator, may be engaged alternatively with a power driven pulley 27 6 For example,

amplifying devices may be provided wherever they may be found necessary or desirable, such as between the piezo-electric oscillator 10 of the transmitter and the phaseshifting means 12. Moreover, the phase of the oscillations produced at the receiver by the local piezo-electric oscillator of either Fig. 2 or B'may be such as to neutralize the oscillations received from the transmitter either in the open or closed position of the key 98 or in any desired position of the rotor coil 62, and the indicator 142 or 242 maybe caused to operate either upon reception of unneutralized energy from the transmitter or upon neutralization of the received oscillations by the oscillations produced by the 10- cal piezo-electric oscillator. Furthermore, the rotor coil 62 may be manipulated for sig naling purposes through angles different from 180. Accordingly, it is intended that the scope of this invention shall be limited only by the appended claims.

Having fully described my invention, what I claim is:

1. In a system for electrical signaling, a piezo-electric oscillator for generating oscillations of a substantially constant high frequency, means for amplifying the high frequency oscillations, and .means interposed between the piezo-electric oscillator and the amplifying means forehanging the phase of the amplified oscillations by equal amounts and in alternately opposite senses in accordance with signals.

2. In a system for electrical signaling, a transmitter a piezo-electric oscillator for generating oscillations of a high frequency substantially constant with narrow limits, means for amplifying the high frequency oscillations, and means interposed between the piezo-electric oscillator and the amplifying lations, and means for electrlcally connecting the piezo-electric oscillator to the gridfilament circuit of said tube, said means comprising apparatus for changing the phase of the amplified oscillations, in accordance with signals.

4. In a system for'electrical signaling, a PIGZO-BLlBCtI'lC OSClllSIOI for generating oscily cona difierent phasein accordance with sign stant within narrow limits, a three-electrode vacuum tube amplifier for increasing the intensity of said oscillations and means for electrically connecting the piezo-electric oscillator to the grid-filament circuit of said tube comprising inductive and capacitive circuits connected in parallel with each other and coupled with the piezo-electric oscillator, a react-ancc device arranged to be coupled with said inductive and capacitive circuits and connected in the grid-filament circuit of said tube, and key-controlled means for differentially coupling the reactance device with said inductive and capacitive circuits to change the phase of the oscillations supplied to the tube in accordance with signals.

5. In a system for electrical signaling a piezo-electric oscillator for generating oscillations of high frequency substantially constant within narrow limits, an amplifier for said oscillations comprising a three-electrode vacuum tube, a closed circuit coupled with said oscillator and comprising inductive and capacitive branches connected in parallel and so constituted that oscillations supplied to said closed circuit will pass through said branch circuits at a difference in phase of substantially 90, alrotor coil arranged to be coupled with said branch circuits respectively and electrically connected with the grid-filament circuit oi the tube, and means for moving said coil angularl to vary the phase of the oscillations supp iecl to said grid-filament circuit in accordance with signals.

6. In a system for electrical signaling, a piezo-electric oscillator for generating oscillations of a high frequency substantially constant within narrow limits, means for normally transmitting said oscillations in one phase, means for changing the oscillations tlo a s and a, receiver for said oscillations comprising an indicator, a piezo-electric oscillator for generating oscillations of the same frequency as those produced by the first-mentioned oscillator, means for causin the last-mentioned oscillator to neutralize t e received oscillations when they are transmitted in one phase and means for causing the received oscillations to operate the indicator in accordance with their phase modifications.

7. In a system for electrical signaling, a transmitter comprising a piezo-electric oscillator for generatingoscillations of a substantially constant high frequency, means for normally transmitting said oscillations in one phase, means for changin the phase of the oscillations alternately an in opposite senses through substantially 180 in accordance transmitter comprising a piezo-electric oscillator for generating oscillations of a substan tially constant high frequency, means for normally transmitting said oscillations in one phase, means for changing the phase of the oscillations alternately and in opposite senses through substantially 180 in accordance with signals and a receiver for said oscillations including a detector, an indicator electrically connected with the output circuit of the detector, a piezo-electric oscillator for generating oscillations of substantially the same frequency as those generated at the transmitter, and means for coupling said lastmentioned oscillator with the detector so as to neutralize said oscillations when they are transmitted in one phase and prevent them from operating the indicator and to permit said oscillations to operate the indicator when they are transmitted in said difierentphase, said last-mentioned means comprising a rotor coil and means for operating the rotor coil to compensate for a difference in the frequencies of said oscillators.

JOHN HAYS HAMMOND, JR. 

